Life History of the Caligid Copepod 
Lepeophtheirus dissimulatus Wilson, 1905 (Crustacea: Caligoida) 1 
Alan G. Lewis 2 
Copepods of the family Caligidae are found as 
external parasites on both fresh and salt water 
fishes throughout the world. Even with their 
wide distribution, relatively little is known 
about their life history. The presentation of the 
life history of Lepeophtheirus dissimulatus , a 
caligid found on salt water fishes, should pro- 
vide more information on the life history and 
general biology of this group of copepods. 
Although there are many references to im- 
mature and juvenile or larval stages (reviewed 
by Heegaard, 1947 : 2 1-3 1 ) , only a few workers 
have had the material to describe the complete 
life history of a caligid. Through methods de- 
scribed below, the author was able to obtain a 
series of Hawaiian specimens representing all 
of the stages of development of L. dissimulatus. 
Lepeophtheirus dissimulatus is one of the 
more common parasitic copepods of Hawaiian 
acanthurid (surgeon) fishes. The species is not 
limited only to Hawaiian fishes but is known 
from a wide variety of localities and a wide 
variety of hosts (Lewis, in press). Even with 
its wide distribution, in both the Atlantic and 
Pacific oceans, larval stages have been described 
only once, by Shiino (1959:309), from fishes 
of the Revilla Gigedo Islands. 
Attempts to rear the copepod from the egg to 
the adult in culture were only partially success- 
ful. Ovigerous adult females were placed in clean 
finger bowls partially filled with cotton-filtered 
or unfiltered sea water. Circulation of the water 
was accomplished by means of a fine jet of 
air from a slender glass tube immersed in the 
medium. The water was changed at least once 
1 A portion of a thesis submitted to the University 
of Hawaii in partial fulfillment of the requirements 
for the degree of Doctor of Philosophy. Contribution 
number 181, Hawaii Marine Laboratory. Manuscript 
received November 23, 1961. 
2 Department of Zoology, University of New Hamp- 
shire, Durham, New Hampshire. 
every 8 hr and usually more frequently. At the 
time the eggs, carried by the female, hatched, 
a portion of the first nauplii, the first larval 
stage, was removed with a wide-mouthed pipette 
and placed in small stender dishes. The remain- 
ing nauplii were left in the finger bowl and 
the adult female was removed and placed in a 
separate bowl. Water in the finger bowls was 
circulated in the same manner as above and 
changed at the same time intervals. Water in 
the stender dishes was not circulated but instead 
was changed at more frequent intervals, every 
3-4 hr. As moulting occurred into the second 
naupliar stage, the newly moulted second nau- 
plii were transferred to new finger bowls or 
stender dishes except for three to four indi- 
viduals which were preserved in either 10% 
buffered formalin or 95% ethyl alcohol. Shortly 
after the second naupliar stage moulted into the 
succeeding stage, the copepodite, a piece of 
loosely woven nylon cloth was placed in the 
dishes to offer a substrate for attachment. (It 
was found that the copepodite stage is the stage 
which attaches to the host.) In addition, pieces 
of host tissue were placed in some of the dishes. 
The host tissue was left in the dishes for 1 hr 
and then removed and the animals transferred 
to a new dish in order to reduce contamination 
and bacterial action. 
The mortality rate between the first and sec- 
ond naupliar stages was high and appeared to 
be partially due to the inability of the nauplius 
to break out of the old cuticle. The rate from 
the second naupliar stage to the copepodite was 
relatively low. Out of the 30 attempts that were 
made to rear the copepod, each with at least one 
female carrying from 20-60 eggs, one copep- 
odite was obtained that attached to the nylon 
cloth placed in the dish. The remaining copep- 
odites died without attaching and the single 
copepodite that attached died immediately 
thereafter. None of the copepodites attached to 
the host tissue placed in the dishes. 
195 
